In this work, the Foucault knife-edge test, which has traditionally been known as the classic test for optical imaging
devices, is used to characterize an acoustic lens for operation at 1.2 GHz. A confocal laser scanning microscope (CLSM)
was used as the illumination and detection device utilizing its pinhole instead of the classical knife edge that is normally
employed in the Foucault test. Information about the geometrical characteristics, such as the half opening angle of the
acoustic lens, were determined as well as the quality of the calotte of the lens used for focusing. The smallest focal spot
size that could be achieved with the examined lens employed as a spherical reflector was found to be about 1 μm. By
comparison to the idealized resolution a degradation of about a factor of 2 can be deduced. This limits the actual quality
of the acoustic focus.
The biomaterial chitosan is used in the paper manufacturing industry, as a wound healing agent and in filtration amongst
others. In this paper the longitudinal sound velocity and acoustic impedance of thin films of chitosan of varying
thicknesses are determined by vector-contrast acoustic microscopy. The exploitation of the relative reflectivity
information from the maximum amplitude images and a comparison of the experimentally obtained V(z) curves with simulations using appropriate models are applied for the evaluation of the sound velocity. These results were compared to those previously obtained results with the same instrument.
With the aid of phase contrast acoustic microscopy, the material properties related to mechanics including the speed of
ultrasonic waves can be determined. For this purpose the observed variation of the magnitude and phase with the
variations in the thickness of the sample in transmission is complemented by modeling in reflection. The later relates to
the observation of interference. In the application presented here involving acoustical waves, also time resolved
generation and detection is employed to suppress interferences for sufficiently extended objects. This allows the
determination of the desired mechanical properties by first arrival techniques. Both methods, interference and first
arrival, are presented and discussed. Applications involve also observations on microscopic scales with a lateral
resolution of 1 μm. Some of the principles involved for modeling at the resolution limits are exemplified here also on larger scales to demonstrate the reliability of the developed schemes.
Microscopic objects including living cells on a planar substrate are investigated in bio-medical applications of scanning
acoustic microscopy. Beside of the observation of lateral structures, the determination of sample properties such as
density, sound velocity, and attenuation is desired, from which elastic properties can be derived. This can be achieved
with the aid of the acoustic phase and magnitude contrast represented in a polar plot. For homogeneous and sufficiently
planar objects the contrast in magnitude and phase is a function of the properties of the substrate and the coupling fluid,
which both can easily be determined, and of the mechanical properties of the sample under observation. For observation
in reflection and variable thickness of the sample the signal will depend on the actual thickness. This signature of the
object can be fitted based on a conventional ray model for the sound propagating in the coupling medium and the
sample. The model includes also the refraction and reflection at all interfaces between transducer, lens material, coupling
fluid, object, and substrate. The method is demonstrated for a chitosan film deposited on a glass substrate. The scheme
presented here is capable to reach a resolution of about and even below 1% for relevant quantities in applications
involving imaging at 1.2 GHz in aqueous coupling fluids.
Acoustic and optical multiple contrast microscopy has been employed in order to explore characterizable parameters of
red blood cells, including cells infected by the parasite Plasmodium falciparum, in order to investigate cellular
modifications caused by the infection and to identify possible detection schemes for disease monitoring. Imaging
schemes were based on fluorescence, optical transmission, optical reflection, and amplitude and phase of ultrasound
reflected from the cells. Contrast variations observed in acoustic microscopy, but not in optical microscopy, were
tentatively ascribed to changes caused by the infection.
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